Systems and methods for detecting tissue contact and needle penetration depth using static fluid pressure measurements
Systems and methods for determining tissue contact and penetration depth are provided. In one aspect, the system includes a needle and a pressure measurement assembly. The needle, in one exemplary embodiment, includes a first end and a second end with at least one aperture located a predetermined distance from the first end. The fluid pressure measurement assembly is connected with a portion of the needle to measure pressure of fluid dispensed in the needle. The fluid pressure measurement assembly measures a first pressure of the fluid, a second pressure when the needle contacts tissue and a third pressure when the needle penetrates the tissue and the aperture becomes occluded.
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This is a continuation in part of U.S. patent application Ser. No. 10/166,854, filed on Jun. 10, 2002. The application Ser. No. 10/166,854 is hereby incorporated by reference in its entirety.
FIELDThe invention relates generally to needles, and more particularly, to a system and method for detecting tissue contact and needle penetration depth.
BACKGROUNDDrug delivery systems currently exist that supply therapeutic substances through a needle to regions of a patient's body. Such regions may include a diseased blood vessel, body cavity or organ. In the case of a diseased blood vessel, for example, the therapeutic agent may be used to treat an arterial lesion and/or to promote an angiogenic response
In some applications, a needle may be connected to a catheter assembly to deliver the therapeutic agent deep into the body. In this application, it is often difficult to determine when the needle contacts the organ, cavity wall, or vessel wall. Further, it is difficult to determine the penetration depth of the needle. In many of the applications for which a needle catheter assembly is used to deliver therapeutic agents to regions within the body, the agent must be delivered to a precise location. Accordingly, it is described to provide feedback that indicates when the needle contacts the cavity or vessel wall and when the needle has been inserted to a predetermined depth.
SUMMARYSystems and methods for determining tissue contact and penetration depth are provided. In one aspect, the system includes a needle and a fluid pressure measurement assembly. The needle, in one exemplary embodiment, includes a first end and a second end with at least one aperture located a predetermined distance from the first end. The fluid pressure measurement assembly is connected with a portion of the needle to measure pressure of fluid dispensed in the needle. The fluid pressure measurement assembly measures a first pressure with the fluid dispensed in the needle, a second pressure when the needle contacts the tissue and begins to compress the fluid in the needle and a third pressure when the needle penetrates the tissue further compressing the fluid in the needle, and the aperture becomes occluded.
In an alternative aspect, the system includes a needle and a fluid pressure sensor. The fluid pressure sensor, in another exemplary embodiment, is coupled with a portion of the needle. The needle, in one exemplary embodiment, includes a first end and a second end with at least one aperture located a predetermined distance from the first end. The sensor is connected with a portion of the needle to allow for measurement of pressure of fluid dispensed in the needle. The sensor allows for measurement of a first pressure with the fluid dispensed in the needle, a second pressure when the needle contacts the tissue and begins to compress the fluid in the needle and a third pressure when the needle penetrates the tissue further compressing the fluid in the needle, and the aperture becomes occluded. The fluid pressure sensor is located a predetermined distance from the first end of the needle.
The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which:
Systems and methods for detecting tissue contact and needle penetration depth are described. In the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention. Several exemplary embodiments are described herein, and it will be appreciated that alternative embodiments exist within the scope of this invention.
In
The needle 130 includes a needle tip 132 and an aperture 134 located a predetermined distance from the needle tip 132. As the needle 130 is inserted into body tissue, first the needle tip 132 lumen and then the aperture 134 become occluded. This is shown in
In one embodiment, the fluid is constantly flowing through the needle 130 as the needle 130 is being advanced into the body tissue. The dynamic injection pressure of the fluid is measured. With the fluid constantly flowing through the needle 130, the fluid dynamic injection pressure changes (increases) as the needle tip 132 lumen contacts the body tissue, and changes (increases) again when the aperture 134 becomes occluded. The changes in the fluid dynamic injection pressure indicate the changes in the penetration depth of the needle 130.
In another embodiment, the fluid is dispensed into the needle 130 but not constantly flowing through the needle 130 as the needle 130 is being advanced into the body tissue. The static pressure of the fluid is measured. With the fluid dispensed in the needle 130, a first static pressure is measured. As the needle tip 132 lumen contacts the body tissue, the tissue compresses the fluid within the needle and the static pressure changes (increases) resulting in a second static pressure measurement. As the needle 130 penetrates deeper into the body tissue and the aperture 134 becomes occluded, the static pressure changes (increases) resulting in a third static pressure measurement. The changes in the static fluid pressure (from the first, to second and to the third pressure) indicate the changes in the penetration depth of the needle 130.
In one embodiment the needle 130 may include more than one aperture 134 spaced in predetermined distances from the needle tip new number of the needle 130. For example, a first aperture 134 may be located a first predetermined distance from the needle tip 132. A second aperture (not shown) may be located a second predetermined distance from the first aperture 134. In alternative embodiments, there may be more than two apertures.
In one embodiment, the space between the apertures may be the same. In other alternative embodiments, the distances between the apertures may be different. In another embodiment, the apertures may all be the same size and shape while in another embodiment the sizes and shapes of the apertures could be different. The apertures should be much smaller than the needle tip 132 lumen so that the fluid will be ejected from the needle tip 132 lumen rather than the aperture 134. In one embodiment, the occlusion of both the needle tip 132 lumen and individual aperture 134 and the concomitant increases of fluid pressure allow an operator to determine the penetration depth of the needle 130 as it becomes embedded in the vessel wall 150. The fluid pressure includes the dynamic pressure and the static pressure of the fluid depending on the embodiments. In embodiments where the fluid is constantly flowing through the needle 130 as the needle 130 is advanced into the body tissue, the pressure changes indicate the changes in the dynamic injection pressure of the fluid. In embodiments where the fluid is dispensed through the needle 130 prior to the injection and the fluid is static (e.g., not flowing) through the needle 130 as the needle 130 is advanced into the body tissue, the pressure changes indicate the changes in the static pressure of the fluid as the tissue compresses the fluid in the needle 130. The changes the static fluid pressure or the injection dynamic pressure allow an operator to determine the penetration depth of the needle 130 as it becomes embedded in the vessel wall 150.
In one embodiment, injection pressure measurements are taken continuously as a therapeutic agent is injected from the first end of a needle, through the needle 130, and through the needle tip 132 lumen. The pressure measurements indicate the dynamic injection pressures of the therapeutic agent as the needle 130 is advancing into the tissue. The changes in the dynamic injection pressure indicate the penetration depth of the needle 130.
In an alternative embodiment, a first static fluid pressure is measured when the needle 130 is filled with a therapeutic agent; a second static fluid pressure is measured when the needle tip 132 contacts the vessel wall 150 and as the needle tip 132 lumen becomes occluded; and a third static fluid pressure is measured when the needle 130 advances further into the vessel wall 150 and the aperture 134 becomes occluded. The therapeutic agent is not injected continuously as the needle 130 is being advanced. The pressure measurements indicate the static fluid pressure of the therapeutic agent as the needle 130 is advancing into the tissue. The changes in the static pressure caused by the compression of the fluid by the tissue indicate the penetration depth of the needle 130.
As the vessel wall or other tissue within the body occludes the needle tip 132 lumen, an increase in pressure will occur. Accordingly, an operator is able to determine by the increase in fluid pressure that the needle tip 132 has contacted the vessel wall. As the vessel wall or other tissue occludes the aperture 134, another increase in fluid pressure will occur. An operator is again able to determine by the second increase in pressure that the needle 130 has been inserted to a predetermined depth in the tissue or vessel wall 150.
In one embodiment, the graphs are representative of pressure versus time where it is assumed that the needle 130 is pushed into vessel wall 150 over time in the sequence shown in
As seen in
In one embodiment, the sensor 512 detects a first fluid injection pressure increase as the needle tip contacts tissue. The sensor 512 measures a second fluid injection pressure increase as the needle 130 penetrates the tissue to a predetermined depth. The second fluid injection pressure increase occurs as the aperture in the needle (shown in
In another embodiment, the sensor 512 detects a first static fluid pressure of the fluid in the needle 130. The sensor 512 also detects a second static fluid pressure as the needle tip 132 lumen contacts the tissue. The sensor 512 also determines the static fluid pressure change between the first and the second static fluid pressure (an increase in pressure) to indicate that the needle tip 132 lumen has contacted the tissue and has become occluded. The sensor 512 further measures a third static fluid pressure as the needle 130 penetrates the tissue to a predetermined depth when the aperture 134 in the needle 130 (shown in
An example of a fluid pressure measurement assembly 500 that may be utilized with the present invention is a disposable fluid pressure monitoring system manufactured by Utah Medical Products, Inc. The assembly 500 may easily be attached to a luer lock attached to the proximal end of the needle 130. The disposable fluid pressure monitoring system provides fluid path visualization. Different manufacturers may also produce similar fluid pressure measurement systems that are capable of being utilized in the context of the present invention. Alternatively, a much smaller fluid pressure sensor assembly can be integrated directly into the needle assembly. For example, a smaller version of the sensor 512 could be mounted onto a small plastic connector that is used to attach the needle to the syringe.
In one embodiment, the fluid pressure measurement assembly 500 incorporates a visual feedback system such as the indicator 900 shown in
Next, the signal processor may cause the visual indicator 900 to show a window 904 to indicate that the needle 130 has penetrated the tissue and the needle tip 132 lumen is occluded. The window 904 may be used to indicate that the change in the pressure of the fluid is significant and correlates to the penetration depth of the needle 130 where the needle tip 132 lumen is occluded by the tissue. The magnitude of the increase may be predetermined as shown in
Next, the signal processor may cause the visual indicator 900 to show a window 906 to indicate that the needle 130 has penetrated the tissue to the predetermined distance and that the needle tip 132 lumen as well as the aperture 134 is occluded. The window 906 may be used to indicate that the change in the pressure of the fluid is dramatic or significant and correlates to the penetration depth of the needle 130 where the needle tip 132 lumen as well as the aperture 134 is occluded by the tissue. The magnitude of the increase may be predetermined as shown in
In an alternative embodiment, an audible feedback system is incorporated into the pressure measurement assembly 500 instead of or in addition to the visual feedback system. The audible feedback system may be incorporated similarly to the visual feedback system previously described. Instead of having the visual indicator 900, the sensor 512 may incorporate a convenient audible feedback system. In one embodiment, the audible feedback system is recognizable by human such as a beeping sound. A slow beep may be used to indicate that the needle is filled with a fluid but has not reached the tissue. A faster beep may be used to indicate that the needle tip has penetrated the tissue and has become occluded. An even faster beep may be used to indicate that the needle 130 has reached the predetermined depth of the aperture and that the operator may stop.
In an alternative embodiment, a computer processor (not shown) is coupled to the pressure measurement assembly 500 to measure, calculate, and assess the change or rate of change in the fluid pressure (dynamic or static) in the needle 130. In one embodiment, the computer processor is configured to use the differential amplifier 800 shown in
The syringe pump 612 pumps a therapeutic agent at a constant rate through the needle 130. The therapeutic agent should be pumped very slowly so that the amount of therapeutic agent that is dispensed before the needle reaches the desired penetration depth is minimized. As the needle 130 advances and its tip makes contact with or penetrates tissue, the occlusion of the needle tip creates a first resistance to the flow of the therapeutic agent. This is detected by the pressure sensor 624. Accordingly, the increase in pressure indicates that the needle 130 has contacted tissue.
The operator continues to advance the needle 130 until the tissue begins to occlude the aperture (shown in
In an alternative embodiment, a handheld syringe 618 or another suitable device is used to dispense a therapeutic agent into the needle 130 prior to inserting the needle 130 into the patient. The initial static fluid pressure of the therapeutic agent is measured. As the needle 130 advances and its tip lumen makes contact with or penetrates tissue, the occlusion of the needle tip lumen creates an increase in the static fluid pressure of the therapeutic agent. This is detected by the pressure sensor 624. Accordingly, the increase in pressure indicates that the needle 130 has contacted tissue. The operator continues to advance the needle 130 until the tissue begins to occlude the aperture (shown in
An example of a strain gauge 840 that may be utilized with the present invention is a miniature semiconductor strain gauge manufactured by Entran. These strain gauges may be processed from P-type silicon in orientation, which provide maximum sensitivity to applied strain. Different strain gauges may also be available in other configurations. Different manufacturers may also produce similar strain gauges that are capable of being utilized in the present invention. In order to prevent false signals, the signal from the strain gauge should be offset or calibrated to the appropriate level of force that the tissue is expected to exert during successful tissue penetration. The force exerted by the tissue after successful needle penetration is much greater and longer in duration than accidental contact with the needle sheath, catheter assembly or vessel wall. To minimize false signals further, the force measurements should be taken only after the fluid delivery catheter 700 has reached its intended destination.
Strain gauges are typically mounted very securely to the item that is expected to deform or experience strain. Since the needle 830 is relatively strong, it will not deform during tissue penetration and the securely mounted strain gauge 840 will not produce a signal. In one embodiment, the strain gauge is embedded in a soft polymeric encapsulant 842 before it is mounted on the needle 830. When the soft encapsulant 842 makes contact with tissue during penetration, it deforms and transfers this energy to the strain gauge 840. In one embodiment, the soft polymeric material encapsulant 842 may be made of silicone. In alternative embodiments, the encapsulant 842 may be made of other biocompatible materials.
In one embodiment, the distal portion 834 of the needle 830 may have an outer diameter of 0.008 to 0.26 inches and a proximal portion diameter of 0.012 to 0.3 inches. In alternative embodiments, these dimensions may change according to application.
In one embodiment the piezoelectric transducer 1040 may also be covered by a soft encapsulant material as was shown for the strain gauge discussed above in reference to
At processing block 1120, the needle dispenses a measured amount of therapeutic agent from a second end of a needle to a first end of the needle. At processing block 1130, the dynamic injection pressure of the therapeutic agent in the needle is measured. At processing block 1140, a first increase in the dynamic injection pressure is measured when the first end of the needle contacts tissue. At processing block 1150, a second increase in the dynamic injection pressure is measured as the needle penetrates into the tissue to a predetermined depth.
At processing block 1504, an initial static pressure of the therapeutic agent is measured with the therapeutic agent not flowing through the needle at this point. At processing block 1506, a first change in the static pressure of the therapeutic agent is measured when the needle tip lumen contacts and becomes occluded by the tissue. At processing block 1508, a second change in the pressure of the therapeutic agent is measured when the needle aperture becomes occluded as the needle penetrates the tissue to a predetermined depth.
Systems and methods for detecting tissue contact and needle penetration depth have been described. Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.
Claims
1. A system for detecting tissue contact and penetration depth comprising:
- a needle with a first opening to and in fluid communication with a lumen of the needle and a second opening to and in fluid communication with the same lumen of the needle, said needle having the lumen extending between the first opening and the second opening, and the second opening including at least one aperture in the needle to the lumen located a predetermined distance from said first opening;
- a fluid pressure measurement assembly coupled with a portion of said needle to measure pressure of a fluid dispensed in said needle, said pressure measurement assembly configured to measure no significant change in pressure as compared to a first pressure that is the pressure of said fluid as said fluid is dispensed through said needle at a constant rate, a second pressure that is a significant increase in pressure as compared to the first pressure when said needle contacts said tissue and said first opening becomes occluded, and a third pressure that is a significant increase in pressure as compared to the second pressure when said needle penetrates said tissue and said aperture becomes occluded.
2. The system of claim 1 wherein said pressure measurement assembly comprises:
- a fluid pressure sensor.
3. The system of claim 1 wherein said pressure of fluid includes a pressure of a therapeutic agent to be injected into said tissue.
4. The system of claim 1 wherein said aperture has an area in said range between about 0.003 and 10 mm2.
5. The system of claim 4 wherein said predetermined distance from said first end is about 0.5 to 10 millimeters.
6. The system of claim 1 wherein said predetermined distance is a desired penetration depth of said needle into said tissue.
7. The system of claim 1 wherein said first end of said needle has at least one of a tapered and untapered portion.
8. The system of claim 1 wherein said needle has an outer diameter in said range between about 0.008 and 0.26 inches.
9. The system of claim 1 wherein said needle has an inner diameter in said range between about 0.004 and 0.22 inches.
10. The system of claim 1 further comprises a computer processor coupling to said fluid pressure measurement assembly, said computer processor configured to perform at least one of determining and distinguishing said rate of changes in said static pressure to determine and distinguish said various penetration depths of said needle.
11. The system of claim 10 wherein said computer processor further couples to at least one of a visual feedback system indicator and an audible feedback system to issue human-recognizable signals as to penetration depths of said needle.
12. The system of claim 1 further comprising a signal processor or a computer processor coupled to the fluid pressure measurement assembly to differentiate the third pressure from the first pressure and from the second pressure by detecting the second pressure change when said needle penetrates said tissue said predetermined distance and said aperture becomes occluded.
13. The system of claim 1 further comprising a circuit to differentiate between: (1) a first pressure indicating that the needle has not reached the tissue; (2) a second pressure indicating that the needle has penetrated the tissue and the first opening has become occluded based on a change in pressure or a rate of change in pressure to a significantly larger magnitude; and (3) a third pressure indicating that the needle has penetrated the tissue by the predetermined distance and that the aperture is occluded based on a change in pressure or a rate of change in pressure to a significantly larger magnitude.
14. The system of claim 13 further comprising:
- a visual indicator or an audible feedback system to indicate that the needle has not reached the tissue when the first pressure is measured;
- to indicate that the needle has penetrated the tissue and the first opening has become occluded when the second pressure is measured; and
- to indicate that the needle has penetrated the tissue by the predetermined distance when the third pressure is measured.
15. The system of claim 13 wherein the first opening is in a tip of the needle.
16. The system of claim 1 further comprising a visual indicator or an audio feedback system that indicates to an operator:
- (1) to advance the needle in response to the fluid pressure measurement assembly measuring no significant change in pressure as compared to the first pressure, (2) to proceed with the advancement of the needle slowly in response to the fluid pressure measurement assembly measuring the significant increase in pressure as compared to the first pressure, and (3) to stop the advancement of the needle because the penetration depth desired has been achieved in response to the fluid pressure measurement assembly measuring the significant increase in pressure as compared to the second pressure.
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Type: Grant
Filed: Sep 5, 2003
Date of Patent: Nov 5, 2013
Patent Publication Number: 20040260240
Assignee: Advanced Cardiovascular Systems, Inc. (Santa Clara, CA)
Inventor: Dagmar Beyerlein (San Francisco, CA)
Primary Examiner: Bhisma Mehta
Assistant Examiner: Bradley Osinski
Application Number: 10/656,491
International Classification: A61M 1/00 (20060101);